It can be anything! An apex, subdomain, or even a URL.

Results fordev.user.noextraining.com

Logged At	Not Before	Not After	Common Name	Matching Identities	Issuer Name
2023-05-12T04:01:12.231	2023-05-12T03:01:11	2023-08-10T03:01:10	dev.user.noextraining.com	dev.user.noextraining.com	C=US, O=Let's Encrypt, CN=R3
2023-05-12T04:01:12.003	2023-05-12T03:01:11	2023-08-10T03:01:10	dev.user.noextraining.com	dev.user.noextraining.com	C=US, O=Let's Encrypt, CN=R3
2023-02-21T04:44:34.189	2023-02-21T03:44:33	2023-05-22T03:44:32	dev.user.noextraining.com	dev.user.noextraining.com	C=US, O=Let's Encrypt, CN=R3
2023-02-21T04:44:33.997	2023-02-21T03:44:33	2023-05-22T03:44:32	dev.user.noextraining.com	dev.user.noextraining.com	C=US, O=Let's Encrypt, CN=R3